Digital computer systems are being used today to perform a wide variety of tasks. Many different areas of business, industry, government, education, entertainment, and most recently, the home, are tapping into the enormous and rapidly growing list of applications developed for today's increasingly powerful computer devices.
Modern computer systems usually feature powerful digital processor integrated circuit devices. The processors are used to execute software instructions to implement complex functions, such as, for example, 3-D graphics applications, voice recognition, data visualization, and the like. The performance of many these applications is directly benefited by more powerful, more capable processors. Additionally, powerful modern computer systems have decreased in cost such that they are more available to an average user than ever before.
A primary characteristic of the increasing power of modern computer systems and their decreasing cost is the steady progress of integrated circuit device manufacturing technologies. Modern semiconductor manufacturing technologies lead to increasing levels of integration, increasing power, and decreasing cost of the computer devices (e.g., laptop computer systems, desktop computer systems, workstations, servers, etc.).
Computer system device manufacturers have discovered that compact size is a desirable market trait. Typically, the more compact a device is, the lower its costs of manufacture. Additionally, compact size (e.g. increasing integration) yields a number of other benefits, such as decreased power consumption and increased portability. Accordingly, a primary objective of many computer system device manufacturers is to reduce the form factor of a given device while maintaining, or even increasing, the performance of the device.
The objective of reducing computer system device form factor has led to several prior art integrated circuit packaging schemes. One prior art packaging scheme involves the implementation of multichip modules. A multichip module, or MCM, refers to a chip package that contains two or more “raw” chips closely connected with high-density lines, or signal traces embedded within, or on, the package. A raw chip generally refers to a semiconductor integrated circuit die without its associated packaging. The raw chips are typically mounted directly on or embedded within a base. A prior art MCM implementation saves space and can, in some cases, speed processing due to short leads between chips (e.g., in comparison to several discrete chips mounted conventionally on a printed circuit board). A ceramic base is typically used with chips wire bonded together (MCM-C) or with deposited thin film interconnects (MCM-D). MCMs have been mounted onto silicon substrates (MCM-S) and resin-based, laminated printed circuit boards (MCM-L), the latter, less-costly version evolving into the multichip package (MCP).
Another prior art packaging scheme involves the implementation of multichip packages. A multichip package, or MCP, refers to a chip package that contains two or more packaged chips, as opposed to raw chips. It is essentially an MCM that uses a laminated, printed circuit board-like substrate (MCM-L) rather than ceramic (MCM-C).
However, there are a number of problems with the above prior art packaging implementations. With both MCMs and MCPs, it is very difficult to route signal traces through the base or the substrate. For example, modern processor integrated circuit dies can have 500 or more interconnects which need to be coupled and routed through the substrate. In an MCM or MCP having a number of such dies, the routing problem can be very substantial.
Other problems arise from the increasing complexity forced upon the design of the substrate. The routing problem causes the design of the substrate to be much more complex. For example, to route thousands of different traces, many substrates are implemented in multiple layers and implement signal traces in a tightly packed manner, which can, in turn, cause another set of problems (e.g., crosstalk, uneven path delay, etc.). Additionally, highly complex substrates are difficult to manufacture. For example, high-performance MCMs mounting multiple chips have very tight manufacturing tolerances. The tight tolerances decrease the yield and reliability of the MCM. This increases the cost of the resulting computer system device. Another factor that increases cost is the use of raw chips. The raw chips must typically be mounted on the substrate and the device essentially finished prior to testing. Thus, it is difficult to detect defective dies prior to device completion. This reduces the overall yield of the device fabrication process.
Another problem with prior art MCM and MCP packaging implementations is the fact that with compactly packaged MCM/MCP devices, it becomes very difficult to manage heat dissipation. It is more difficult to effectively remove heat from the multiple chips. Additionally, the device can be thermally unbalanced wherein heat can spread from “hot” components to “cool” components, affecting their performance and reliability. Also, substrates and ceramic bases of devices are not a very good heat conductors. Consequently, prior art MCM/MCP devices can require complex heat sink apparatuses to maintain high performance levels. Most of the waste heat is required to transfer into the ambient air (e.g., requiring heat pipes, high air flow, noisy fans, etc.). As component packaging density increases and clock speed increases, the thermal energy that must be dissipated also increases. To maintain high-performance, a stable operating temperature must maintained. Accordingly, high performance prior art MCM/MCP devices must be configured for use with elaborate heat dissipation devices (e.g., heat sink fans, liquid cooling, heat spreaders, etc.). This increases the size of the overall package and can counteract a primary benefit of using an MCM/MCP design.
Thus, what is required is a solution that efficiently packages multiple integrated circuit components while maintaining cost effective packaging specifications. What is required is a solution that evidences favorable yield and performance characteristics along with a small package footprint.